Organosilicon compounds have been in use for a long time for the impregnation of mineral construction materials to render them water-repellent
Organofluorine compounds are known for their oil-repellent properties. Although they also possess water-repellent properties, these are substantially less pronounced and their long-term stability is less than that of the organosilicon compounds conventionally used for rendering construction materials hydrophobic.
It was found advantageous to combine both classes of substances. U.S. Pat. No. 4,125,673 and U.S. Pat. No. 5,399,191 describe processes for rendering construction materials oil-repellent and water-repellent with such combination products comprising organosilicon and organofluorine compounds.
One disadvantage of the process described in U.S. Pat. No. 4,125,673 is that either ingredient requires an organic solvent as vehicle or, in the case of aqueous systems, only water-soluble silanes or siliconates can be used. In aqueous media, silanes have the disadvantage of only a very limited and short-lived solubility in water. By contrast, siliconates are highly alkaline and hence not without risk when handled, however, they are only of limited use because they are salts. U.S. Pat. No. 5,399,191 circumvents these difficulties by using special organosilicon compounds with ammonium functional groups, which are water-soluble or water-dispersible. However, these compositions have the disadvantage that they are expensive to manufacture and that the polysiloxanes with ammonium functional groups are incompatible with numerous organofluorine components or, due to polar interactions, interfere with the film formation of the organofluorine component
FR-A-2 639 353 describes compositions consisting of emulsified organosilicon and organofluorine compounds. However, as well as the water-repellent organosilicon component and the oil-repellent organofluorine component, these compositions also contain an organic polymer dispersion for stabilizing the composition. The disadvantage of this component is that it imparts coating properties to the composition, thereby greatly reducing the permeability to water vapor.